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Journal of Drug Delivery and Therapeutics

Open Access to Pharmaceutical and Medical Research

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Open Access Full Text Article   Research Article

Formulation and development of capsules containing dry extracts from the calyces of Hibiscus sabdariffa L. and the sheaths of Sorghum caudatum H., intended as a dietary supplement

Hermine ZIME DIAWARA ¹, Mimtiri S. ZONGO ², Ousseni SAWADOGO ⁶, Luc ZONGO ^2,3,4, Salfo OUEDRAOGO ⁵, Modeste W. OUEDRAOGO ², Heiko LANGE ^7,8, Eloi PALE ⁶, Rasmane SEMDE ¹

1. Laboratoire de Développement du Médicament (LADME/CEA-CFOREM), Université Joseph KI-ZERBO (UJKZ), Ouagadougou, Burkina Faso
2. Hôpital Saint Camille de Ouagadougou (HOSCO), 09 BP 444 Ouagadougou 09, Ouagadougou, Burkina Faso. 
3. Faculté des Sciences de Santé, Université Saint Thomas d’Aquin (USTA), 06 BP 10212 Ouagadougou 06, Burkina Faso.
4. Centre de Recherche Biomoléculaire Pietro Annigoni (CERBA) 01 BP 216 Ouagadougou 01, Burkina Faso.
5. Département de Médecine et Pharmacopée Traditionnelles-Pharmacie (Mephatra-PH), Institut de Recherche en Science de la Santé (IRSS/CNRST), 03 BP 7047 Ouaga 03, Burkina Faso.
6.  Department of Chemistry Doctoral School of Sciences and Technology, University Joseph KI-ZERBO, Laboratory of Analytical, Environmental and Organic Chemistry (LCAEBiO), Research Team: Applied Organic Chemistry (ECOA), Ouagadougou BP 7021, Burkina Faso  
7. University of Milano-Bicocca, Department of Earth and Environmental Sciences, Piazza della Scienza 1, 20126 Milan, Italy.
8. NBFC – National Biodiversity Future Center, 90133 Palermo, Italy.

 

 

Medicinal plants are a major source of bioactive substances used in therapy.^1,2 Beyond their physiological roles in plants, defense against biotic and abiotic stressors and facilitation of reproduction, these metabolites also exert relevant effects in the human body.³ Advances in organic chemistry during the second half of the twentieth century enabled the extraction and standardization of these compounds for medical and nutritional use.⁴ In industrialized countries, interest in phytomedicine has grown in response to modern exposures (environmental pollutants, alcohol, medications, ultraviolet radiation, tobacco), which promote oxidative stress and metabolic disorders.^5,6

Oxidative stress is ambivalent: while reactive species are essential for cellular signaling, detoxification, and host defense, their excess contributes to the onset or progression of many diseases (cancer, cataract, pulmonary edema, accelerated aging).⁷ Preventing redox imbalance with antioxidants—substances capable of preventing or slowing the oxidation of other molecules—has therefore become a public-health and research priority.^8,9 Numerous plant extracts exhibit documented free-radical-scavenging activity,¹⁰ notably the calyces of Hibiscus sabdariffa Lemordant, D. and the sheaths of Sorghum caudatum (Hack.) Stapf, valued for their richness in anthocyanins and other polyphenols with potential roles in preventing oxidative-stress-associated pathologies.^11–13 Accordingly, antioxidants aim to reduce the risk of various diseases¹⁴ and represent a scientific and societal priority by reinforcing endogenous defenses against oxidative stress.¹⁵

However, anthocyanins, water-soluble pigments ranging from red to blue, often show limited bioavailability and instability toward pH, temperature, and light, which may attenuate in vivo effects.^16–20 Dietary intakes vary widely and do not, by themselves, ensure optimal exposure.^21,22 Moreover, quantitative extraction and purification are challenging (influenced by pH, solvent, temperature, and solid-to-solvent ratio) and must rely on food/industry-compatible processes (acidified ethanol and/or water).^23,24 In this context, pharmaceutical formulation of standardized oral solid forms can improve stability, dose reproducibility, and clinical acceptability of anthocyanin-rich extracts.

Preliminary work at the Laboratory of Organic Chemistry and Applied Physics, Joseph KI‑ZERBO University (Burkina Faso), has established extraction and quantification of total anthocyanins, total polyphenols, and antioxidant activity from H. sabdariffa and S. caudatum extracts.^25,26 In line with regulatory definitions, food supplements are foods intended to supplement the normal diet and constitute concentrated sources of nutrients or other substances with nutritional or physiological effects, alone or in combination.²⁷ Developing capsules containing purified dry extracts of locally available antioxidant-rich plants thus aligns with a strategy of nutritional prevention under quality-assured conditions.

The study tests the hypothesis that standardizing and encapsulating purified dry extracts from the calyces of Hibiscus sabdariffa and the sheaths of Sorghum caudatum will produce stable, dose-reproducible oral dosage forms suitable for dietary supplementation, while preserving the antioxidant functionality of their anthocyanins. In line with this hypothesis, the work seeks to advance capsule-based food supplements from these extracts by formulating optimized capsules for each plant, manufacturing pilot experimental batches, and performing comprehensive quality control on both the extracts and the finished capsules, covering compliance, quantitative assay, and technological performance, to maximize anthocyanin stability and ensure accurate dosing.

2. MATERIALS AND METHODS
   2.  Study design and setting

The experimental study was carried out in Ouagadougou, Burkina Faso, from November 2022 to August 2023. Extraction, characterization, and analytical assays were performed at the Laboratory of Organic Chemistry and Applied Physics (LCOPA, UFR/SEA). Powder and capsule quality control were conducted at the Galenics Laboratory of the Department of Traditional Medicine–Pharmacopoeia and Pharmacy (MEPHATRA/PH) at IRSS. Lyophilization, capsule preparation, and additional quality control took place at the Drug Development Laboratory (LADME) of Joseph KI-ZERBO University. Milling of the plant material was undertaken at the Department of Natural Substances of IRSAT.

2. Materials
   • Plant materials and sample preparation

Calyces of Hibiscus sabdariffa Lemordant, D. (bissap) were purchased as mixed-lot (“tout-venant”) samples from Ouagadougou markets (August 2021, March 2022). Dry sheaths of Sorghum caudatum (Hack.) Stapf (red sorghum) were available at LCOPA. Calyces and sheaths were milled to powder using an electric grinder at IRSAT and stored desiccated until use.

Balances: analytical (max 160 g, d = 0.1 mg; METTLER TOLEDO, Switzerland) and precision (max 1500 g, d = 0.1 g; METTLER, Switzerland); freeze-dryer (Alpha 1-4 LSC basic, CHRIST, Germany); rotary evaporator (BUCHI, Heating Bath B-300); disintegration tester (SOTAX DT2); pH meter (WTW 3210 SET3); halogen moisture analyzer (RADWAG); hotplate (DIAB MS-H280 Pro); powder flow tester (diameter/angle). Capsule shells (size 0), semi-automatic capsule filler, and opaque plastic bottles were used for manufacturing and packaging. Standard laboratory glassware (graduated cylinders, beakers, mortars/pestles, spatulas, filter papers) were employed.

Colloidal silica (Aerosil® 200, Fagron, Saint-Denis); maize starch (diluent); aluminum chloride (LABKEM, 25 °C); standards: Trolox, quercetin, tannic acid; solvents: distilled water, absolute ethanol, absolute methanol; Amberlite XAD-7 resin; trifluoroacetic acid (TFA). Buffers for spectrophotometry are specified below.

2. Methods 
   • Extraction Methods and Dry Extract Characterization

Plant powders were processed to yield three extract types: a lyophilized aqueous extract from Hibiscus sabdariffa calyces, a purified phenolic-rich extract from the same calyces, and a purified phenolic-rich extract from Sorghum caudatum sheaths. Each extract then served as the active ingredient for its corresponding capsule formulation.

One hundred grams of calyx powder were macerated in 300 mL of water for 24 h at 4 °C. The aqueous extract was centrifuged and filtered through paper; the process was repeated three times. Combined filtrates were lyophilized. The lyophilizate was stored at 4 °C in sterile bottles pending qualitative and quantitative analyses.

A second batch of 100 g of calyx powder was macerated in 300 mL of water; after centrifugation, the filtrate was percolated over an Amberlite XAD-7 column. Phenolics were adsorbed onto the resin, while mineral salts, sugars, and free organic acids were removed by extensive water washing. Phenolic compounds were eluted with ethanol acidified with 1% TFA to afford a phenolic-rich aqueous fraction, which was concentrated under reduced pressure (< 40 °C) to near dryness using a BUCHI rotary evaporator. The concentrate was redissolved in ethanol and precipitated in neat ethyl acetate. The precipitate was vacuum-dried and stored at 4 °C for analyses.

One hundred grams of sheath powder were macerated for 24 h in 400 mL of acidified ethanol (ethanol: TFA 99:1, v/v). The extract was centrifuged and filtered; the process was repeated three times. Combined filtrates were concentrated under vacuum to near dryness, taken up in 15 mL ethanol, and precipitated into acidified distilled water. The precipitate was vacuum-dried and stored at 4 °C for analyses.

Extraction yield (R, %) was calculated as the mass of dry extract obtained divided by the initial 100 g of plant powder, multiplied by 100: R (%) = (mass of dry extract / 100 g) × 100.

Color, taste, odor, and general appearance were recorded by direct observation.

Angle of repose (α) was determined by funnel method (standard orifice), recording cone height and diameter after discharge. Compressibility (Carr index) and Hausner ratio were computed from untapped volume (V₀) and tapped volume (Vf) measured in a graduated cylinder: Carr index (%) = 100 × (V₀ − Vf) / V₀; Hausner ratio = V₀ / Vf. Results were interpreted against European Pharmacopoeia flowability scales.

Approximately 1 g of previously dried powder was placed in a desiccator over a saturated ammonium chloride solution at 25 °C for 24 h. Mass gain (%) was calculated as 100 × (m₃ ‑ m₂) / (m₂ − m₁), where m₁ = mass of empty container, m₂ = mass of container + powder at T₀, and m₃ = mass at 24 h. Classification: deliquescent (solution forms), very hygroscopic (≥ 15%), hygroscopic (≥ 2% and < 15%), slightly hygroscopic (≥ 0.2% and < 2%).

About 1 g of each dry extract was weighed in triplicate watch glasses and dried in an oven at 105 ± 2 °C for 90 min to constant weight. Residual moisture (%) was computed as 100 × (M₁‑M₂) / M, where M₁ = mass before drying (glass + sample), M₂ = mass after drying (cooled), and M = initial sample mass.

A 1% (w/v) dispersion of each purified or lyophilized extract was prepared in distilled water at 37 °C. After homogenization, pH was measured in triplicate using a calibrated pH meter, rinsing the electrode with distilled water between readings. Mean ± SD values were reported.

Total monomeric anthocyanins were estimated using a SAFAS MP96 microplate spectrophotometer via the differential pH method with two buffers: KCl, pH 1.0 (0.025 M) and acetate, pH 4.5 (0.4 M). For each sample, 30 µL extract were mixed with 210 µL buffer; absorbances were read after 15 min at 510 and 700 nm against a reagent blank. A = (A510‑A700) pH 1.0 − (A510 − A700) pH 4.5. Anthocyanins (mg/L, as cyanidin-3-glucoside) were calculated by Beer–Lambert: [Anthocyanins] = (A × M × D × 1000) / (ε × l), with M = 449.2 g·mol⁻¹, ε = 26900 L·mol⁻¹·cm⁻¹, D = dilution factor, and l = path length (cm).

Total anthocyanins were quantified using a SAFAS DES 190 dual-energy spectrophotometer according to the Stonestreet method, employing buffers at pH 0.6 (KCl, 0.025 M) and pH 3.5 (acetate, 0.4 M). Samples were diluted (1:9, v/v) in each buffer, and absorbance was read after ~30 min at λmax (apigeninidin ≈ 480 nm; path length = 1 cm). Based on A = ε·l·c, concentration was derived from ΔA/Δε·l. Using the established conversion, C (mg/mL) = ΔA × 661 × 10⁻³, then converted to mg/L and expressed as mg per g of dry extract.

Capsules were designed to disintegrate rapidly and release the active extract, using powder blends with suitable flowability.

Quantities obtained after extraction and amounts remaining after physicochemical tests are shown in Table 3.

 

 

Extract	Quantity obtained after extraction (mg)	Quantity available after tests (mg)
Lyophilized dry extract of H. sabdariffa calyces	12990	9006.2
Purified dry extract of H. sabdariffa calyces	5810	847.120
Purified dry extract of S. caudatum sheaths	10440	295.2

 

 

Capsule size was determined from the ratio of powder volume to the planned number of capsules (size ≈ volume per capsule). Although calculations indicated sizes 1–2 for some batches, only size 0 hard gelatin capsules (nominal capacity 0.68 mL) and the corresponding semi-automatic filler were available at LADME. Therefore, batch sizes and excipient quantities were adjusted to fill size 0 capsules appropriately.

Powder volumes of extracts and excipients were measured, then blended by geometric dilution in a mortar. Blends were filled into size 0 capsules using a semi-automatic capsule filler. Empty capsules were separated (body/cap), bodies were filled, and capsules were closed with matching caps. This procedure was applied to all three extract types.

Colloidal silica (Aerosil 200) served as a glidant to improve blend flow and prevent agglomeration. Maize starch acted as an inert diluent/filler to reach the required capsule volume and facilitate homogeneous mixing.

A target daily anthocyanin intake of 2.5 mg was specified. Regarding the Hibiscus sabdariffa lyophilized extract (anthocyanins 11.3 mg/g, i.e., 1.13%), the required extract mass was 221.23 mg/day (10 days: 2212.3 mg). From the inferred bulk density (≈ 428.86 mg/mL; 9006.2 mg ≈ 21 mL), the volume per dose was ~0.515 mL, enabling administration as one size‑0 capsule (0.68 mL) per day; producing 40 capsules required a total fill of 27.2 mL, thus ~6.6 mL of maize starch was added as diluent. 

For the purified H. sabdariffa extract (83.91 mg/g; 8.39%), the daily extract requirement was 30.12 mg (10 days: 301.20 mg); with an inferred bulk density of ~84.12 mg/mL (847.12 mg ≈ 10 mL), the per-dose volume was ~0.351 mL, also suitable for one size-0 capsule per day; manufacturing 20 capsules (total 13.6 mL) required ~6.58 mL of excipient consisting of Aerosil 200 (0.69%) plus maize starch. 

Concerning the purified Sorghum caudatum extract (317.77 mg/g; 31.77%), the daily extract need was 7.88 mg (10 days: 78.8 mg); using an inferred bulk density of ~26.84 mg/mL (295.2 mg ≈ 11 mL), the per-dose volume was ~0.30 mL, again compatible with one size-0 capsule per day; producing 30 capsules (20.4 mL) required ~11.52 mL of excipient with Aerosil 200 at 0.37% plus maize starch. 

The resulting batch compositions were as follows: H. sabdariffa lyophilized—8983.65 mg extract and 3405.1 mg maize starch, q.s. to 40 size-0 capsules (1 cap/day); purified H. sabdariffa, 694.67 mg extract, 7.01 mg Aerosil 200, and 305.69 mg maize starch, q.s. to 20 size-0 capsules (1 cap/day); purified S. caudatum, 266.63 mg extract, 2.98 mg Aerosil 200, and 544.4 mg maize starch, q.s. to 30 size-0 capsules (1 cap/day).

Filled capsules were packaged in opaque white plastic bottles and labeled with: laboratory name, preparation name, composition, manufacturing date, expiry date, and batch number.

Quality control was performed according to European Pharmacopoeia (6th ed.) requirements, including macroscopic inspection, uniformity of mass, and disintegration testing.

Appearance, color, and sealing integrity of capsules were recorded.

Twenty capsules were randomly selected and weighed individually (filled), then emptied and the shells weighed. Net fill mass per capsule was computed by difference; the mean mass was compared with pharmacopeial limits (Table 4).

 

 

Dosage Form	Mean mass [mg]	Permitted deviation [% of mean]
Capsules, uncoated granules and powders (unit dose)	< 300 mg	± 10% (max 2 units outside; none beyond limits)
	≥ 300 mg	± 7.5% (max 2 units outside; none beyond limits)

 

 

 

Six capsules were tested in water at 37°C using a standard disintegration apparatus (mesh-bottom tubes with optional disk). Disintegration was defined as the absence of palpable core, with only soft residue or envelope fragments remaining. Compliance was verified against the specified time limit per Ph. Eur.

3.  RESULTS 
   3. Physicochemical Characterization of Dry Extracts

      • Macroscopic and Organoleptic Properties

Macroscopic and organoleptic characteristics of the lyophilized and purified extracts of Hibiscus sabdariffa and the purified extract of Sorghum caudatum, Stapf are summarized below. The lyophilized H. sabdariffa extract appeared dark red, with a characteristic odor and a very sour taste, presenting a porous aspect. The purified H. sabdariffa extract was bright red with a characteristic odor, a sour taste, and a fine powder aspect. The purified S. caudatum extract was red with weakly characteristic odor and taste and a moderately fine powder aspect.

Flow indices derived from angle of repose, Carr’s compressibility index, and Hausner ratio indicated distinct behaviors across extracts. The lyophilized H. sabdariffa extract exhibited fairly good flow, whereas the purified H. sabdariffa and purified S. caudatum extracts showed extremely poor and poor flow, respectively.

 

 

Extract	Angle of repose (°)	Carr's index (%)	Hausner ratio	Flowability
Lyophilized H. sabdariffa	37.5	20.00	1.25	Fairly good
Purified H. sabdariffa	66.5	39.13	1.64	Extremely poor
Purified S. caudatum Stapf	48.5	28.20	1.39	Poor

 

 

All extracts were classified as hygroscopic (mass gain ≥ 2% and < 15%). Mean ± SD values were 5.88±1.10% for lyophilized H. sabdariffa, 7.45±1.80% for purified H. sabdariffa, and 3.51±0.06% for purified S. caudatum.

Residual moisture contents were 6.00±0.03% for lyophilized H. sabdariffa, 5.60±0.01% for purified H. sabdariffa, and 8.28±0.05% for purified S. caudatum, all below the 10% specification.

Measured pH values were 4.4 (lyophilized H. sabdariffa), 4.9 (purified H. sabdariffa), and 5.3 (purified S. caudatum), indicating acidic profiles for all extracts.

Total anthocyanins were lowest in the lyophilized H. sabdariffa extract (11.33±0.49 mg/g), higher in the purified H. sabdariffa extract (83.91±0.15 mg/g), and highest in the S. caudatum extract (317.77±10.07 mg/g). The purified H. sabdariffa extract contained approximately eightfold more anthocyanins than the lyophilized counterpart.

From 100 g of plant powder, yields were 22.6% for lyophilized H. sabdariffa, 8.1% for purified H. sabdariffa, and 6.3% for purified S. caudatum.

3.  Capsule Formulation, Manufacturing, and Packaging

   • Formulations and Manufacturing

Formulations combined pharmaceutical excipients with active extracts, accounting for anthocyanin content determined previously. Batch compositions and pack sizes are reported below.

 

 

Extract	Active (mg)	Aerosil 200 (mg)	Maize starch (mg)	Pack size
H. sabdariffa lyophilized	8983.00	-	3405.10	40 caps, size 0
H. sabdariffa purified	694.67	7.01	305.69	20 caps, size 0
S. caudatum purified	266.789	2.98	544.40	30 caps, size 0

 

 

Capsules were packaged in opaque white secondary boxes with corresponding labels. Label codes were: BL (bissap, lyophilized), BP (bissap, purified), and SP (sorghum, purified).

 

 

3.  Quality Control of Capsules

   • Macroscopic Characteristics

All capsules were cylindrical, smooth, clean, and properly sealed. Color was dark red for lyophilized H. sabdariffa, bright red for purified H. sabdariffa, and red for purified S. caudatum.

Individual capsule masses met pharmacopeial criteria. Mean (±SD) net fill masses (n = 20) were 0.4344±0.0093 g for lyophilized H. sabdariffa, 0.2259±0.0064 g for purified H. sabdariffa, and 0.2755±0.0108 g for purified S. caudatum; all were compliant.

All formulations disintegrated within the 15-minute limit. Mean (±SD) disintegration times (n = 6) were 3.60±0.41 min for lyophilized H. sabdariffa, 3.91±0.13 min for purified H. sabdariffa, and 2.88±0.26 min for purified S. caudatum; the purified S. caudatum capsules disintegrated fastest.

4. DISCUSSION

   4.  Study Limitations

This work aimed to develop capsule formulations using dry extracts from the calyces of Hibiscus sabdariffa L. and the sheaths of Sorghum caudatum H. as dietary supplements, while characterizing key physicochemical parameters. Several limitations should be noted. First, granulometric analysis of the plant powders prior to extraction, required to confirm particle‑size distributions, was not performed because insufficient material was available. Second, microbiological testing of either the bulk extracts or finished capsules was not conducted. Third, post-formulation flow testing of the new blends was not undertaken, and the total anthocyanin content of the finished powders/capsules was not assayed to verify label claim. These gaps should be addressed in subsequent work to strengthen manufacturability and quality assurance.

4. Physicochemical Characterization of Dry Extracts

   • Macroscopic and Organoleptic Attributes

Visual, tactile, and gustatory inspection differentiated the three extracts. The lyophilized H. sabdariffa extract was porous, dark red, and characteristically fragrant with a very sour taste; the purified H. sabdariffa extract was bright red, fine, and similarly characteristic in odor with a sour taste; the purified S. caudatum extract was moderately fine, red, with weakly characteristic odor and no specific taste. These findings indicate partial preservation of plant‑specific sensory signatures. The chosen extraction approaches,²⁵ notably lyophilization, appear to have contributed positively to organoleptic retention despite higher cost, which is consistent with the recognized ability of freeze-drying to better preserve color, odor, and taste.

Aqueous pH values were acidic across extracts (≈4.4 for lyophilized H. sabdariffa; ≈4.9 for purified H. sabdariffa; ≈5.3 for purified S. caudatum). Such acidity is broadly compatible with gastric pH and may mitigate irritation while favoring rapid gastric dissolution and subsequent absorption, noting that pH is a determinant of gastrointestinal drug absorption.²⁸

Residual moisture contents were below 10% for all extracts (≈6.0% lyophilized H. sabdariffa; ≈5.6% purified H. sabdariffa; ≈8.3% purified S. caudatum), complying with European Pharmacopoeia (Ph. Eur.) and Codex limits for dried herbal preparations.²⁹ Lower water content typically confers improved microbiological stability ³⁰ and reduces the likelihood of moisture-driven enzymatic reactions.³¹ Nevertheless, all extracts were classified as hygroscopic (mass gain ≥2% and <15% per Ph. Eur. 6th ed.),³² implying a propensity to absorb ambient humidity during handling and storage. To prevent flow deterioration via agglomeration and ensure dose uniformity, production should occur in humidity-controlled areas, with storage in airtight containers and, where appropriate, inclusion of desiccants.³³

Flow indices (angle of repose, Carr’s index, and Hausner ratio) distinguished the three extracts: the lyophilized H. sabdariffa showed fairly good flow (Hausner ≈1.25), whereas the purified H. sabdariffa and purified S. caudatum exhibited extremely poor and poor flow, respectively (Hausner ≈1.64 and ≈1.39). Particle size and distribution, shape, and density are known to govern flow and dosing behavior.³⁴ In this study, addition of a glidant (Aerosil 200) was necessary to correct poor flow and support reliable capsule filling, thereby improving the prospects for mass uniformity and dose reproducibility.³⁵

All capsules displayed acceptable macroscopic quality, cylindrical, smooth, clean, and non-deformed, indicating appropriate equipment condition and satisfactory process control with the semi-automatic filler. Capsule mass uniformity complied with Ph. Eur. acceptance criteria, supporting consistency of unit doses across batches. Disintegration occurred well within the 15-minute limit, with the purified S. caudatum capsules disintegrating fastest. Given that the shells were gelatin, rapid disintegration is expected and suggests prompt release in the gastrointestinal tract without capsule-derived toxicity.

Formulations combined dry plant extracts as actives with maize starch (diluent/disintegrant) and Aerosil 200 (glidant). Both excipients are widely used in oral solid dosage forms and have no notable adverse effects at the proportions employed.^36–38 Maize starch supports bulk-up to target fill volumes and facilitates disintegration, while colloidal silica improves blend flow by decreasing interparticle cohesion and adsorbing surface moisture.^37–40 Capsules manufacturing offers multiple advantages in this context: masking the acidic taste of the extracts to enhance acceptability; improving dose reproducibility; and protecting anthocyanins, sensitive to heat, oxygen, light, and metal catalysts, from environmental degradation. The use of opaque, oxygen-impermeable secondary packaging further limits oxidative color changes and preserves activity.

Future work will address the current gaps by conducting particle-size analysis (granulometry) of both source powders and finished blends, introducing microbiological testing for bulk extracts and final dosage forms, characterizing post-formulation flow properties, and assaying total anthocyanins in completed capsules to substantiate the label claim. In parallel, stability studies, accelerated and long-term in accordance with ICH guidance, together with water-activity control, dissolution profiling in biorelevant pH media, and content-uniformity testing will be implemented to reinforce quality, manufacturability, and shelf-life projections.

From a formulation standpoint, exploration of alternative fillers (e.g., microcrystalline cellulose) or flow modifiers, optimization of capsule size and fill-weight, and evaluation of desiccant systems may further enhance manufacturability and patient acceptability, while maintaining the intended daily anthocyanin dose.

The primary objective of this study was to develop a solid dosage form using dry extracts from the lyophilized and purified calyces of Hibiscus sabdariffa L. and the purified dry extract from the sheaths of Sorghum caudatum H., formulated with cost-effective, naturally derived excipients. In parallel phytochemical work, anthocyanins were identified as the principal chemical group of interest.

We proposed and produced a capsule dosage form based on these extracts and evaluated the pharmaco-technical characteristics of the three anthocyanin-rich materials. The lyophilized and purified H. sabdariffa extracts exhibited dark-red and bright-red coloration, respectively, with a characteristic mild odor and an acidic taste. The purified S. caudatum extract was red, with a weakly characteristic odor and no distinctive taste.

Pharmaco-technical testing showed that all three dry extracts were hygroscopic. Flow behavior ranged from fairly good for lyophilized H. sabdariffa to extremely poor for purified H. sabdariffa and poor for purified S. caudatum; these deficiencies were improved by incorporating colloidal silica as a glidant.

The final formulation yielded capsules that were cylindrical, smooth, clean, and undeformed, with dark-red, red, or bright-red appearance depending on the extract. Extract fill masses were uniform, averaging 0.4344 g for lyophilized H. sabdariffa, 0.2259 g for purified H. sabdariffa, and 0.2755 g for purified S. caudatum, and each unit was designed to deliver 2.5 mg of active ingredient (anthocyanins). Capsules offer several well-recognized advantages—precise dosing and rapid gastric disintegration among them. The results presented here are experimental and provide a basis for further development.

Conflict of Interest: The authors declare no potential conflict of interest concerning the contents, authorship, and/or publication of this article.

Author Contributions: All authors have equal contributions in revising and editing the manuscript. 

Source of Support: Nil

Informed Consent Statement: Not applicable.

Data Availability Statement: The data presented in this study are available on request from the corresponding author.

Ethical approval: Not applicable

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